Support custom config and params-file in `nextflow config` command

New feature

The nextflow config command is useful for printing the configuration of a project, but could be improved if it also allowed providing custom config files with -c/-C/-params-file just like nextflow run.

Usage scenario

We can run nextflow config main.nf -profile custom_profile to see the configuration that would be used with a subsequent nextflow run command. However, users often wish to supplement or override the config and params with -c, -C, or -params-file when executing a workflow. Allowing nextflow config to accept these arguments would assist users and developers in understanding how the configuration is parsed and prioritized for debugging purposes.

Suggest implementation

Ideally it would re-use the same logic as nextflow run to parse the configuration & parameters, and use the same CLI syntax, e.g.

nextflow config main.nf -params-file custom.yml -C custom.config